Indoor units of air-conditioning apparatuses are installed in rooms (rooms in houses and offices) to be air conditioned. Such an indoor unit is configured to exchange heat between the indoor air suctioned through an air inlet and the refrigerant circulating in a refrigeration cycle with use of a heat exchanger, heats the indoor air in the case of a heating operation, cools the indoor air in the case of a cooling operation, and blows the air back to the room through an air outlet. A blower fan and the heat exchanger are therefore accommodated inside the main body of the indoor unit.
There are various types of indoor units of air-conditioning apparatuses. It is well known that wall type air-conditioning apparatuses having an elongated air outlet and ceiling concealed type air-conditioning apparatuses configured to blow the air in a single direction use a cross flow fan (also referred to as a transverse fan or a transverse flow fan) as a blower fan. For an airflow flowing from the air inlet to the air outlet of an indoor unit of an air-conditioning apparatus, a heat exchanger is disposed at the upstream side of the cross flow fan. That is, a heat exchanger is disposed between the air inlet and the cross flow fan. The air outlet is located at the downstream side of the cross flow fan.
The cross flow fan includes a plurality of impeller elements connected to each other in the rotational axis direction. Each impeller element includes a plurality of blades each having a substantially arcuate shape in the horizontal cross section. The blades are inclined at a predetermined angle and are fixed concentrically to a support plate as a circular (ring-shaped) flat plate having an outer diameter and an inner diameter. A circular end plate to which a rotating shaft supported by a bearing of an indoor unit main body is attached is fixed to a blade end of the impeller element at an end in the rotational axis direction. An impeller element at the other end has a boss-attached side plate that is different from side plates disposed at other portions. The boss-attached side plate includes, at the center thereof, a boss portion to which a motor rotating shaft of a drive motor is attached and fixed. When the drive motor rotates, the cross flow fan rotates about a rotational axis at the center of the rotating shaft. The blade is inclined such that an outer-circumferential edge thereof is located at the front side in the rotational direction.
With the rotation of the cross flow fan, indoor air is suctioned through the air inlet into the indoor unit main body. When passing through the heat exchanger, the air becomes conditioned air whose temperature is adjusted as described above. After flowing through the cross flow fan, the air passes through a flow path leading to the air outlet, and is blown out into the room from the air outlet formed at a lower part of the indoor unit main body.
In this way, the airflow passes between blades twice, in an inlet region at the inlet side of the cross flow fan and in an outlet region at the outlet side. The blade of the cross flow fan has a blade pressure surface at the rotational direction side on which pressure is made greater by the rotation of the cross flow fan than that during rest, a blade pressure suction surface in a counter-rotational direction on which pressure is made less by the rotation of the cross flow fan than that during rest, and two edges connecting the blade pressure surface and the blade pressure suction surface at the outer circumferential side and the inner circumferential side, respectively. An edge located on a far side with respect to the rotational axis of the cross flow fan is a blade outer-circumferential edge, and an edge located on a near side of the rotational axis is a blade inner-circumferential edge. In the inlet region of the cross flow fan, the air flows from the blade outer-circumferential edge toward the blade inner-circumferential edge. In the outlet region, the air flows from the blade inner-circumferential edge toward the blade-outer circumferential edge.
In recent years, air-conditioning apparatuses have been required to have greater capacity so as to be effective for larger rooms, and therefore the cross flow fans have been required to achieve greater air volume. Further, the air-conditioning apparatuses have also been required to provide energy-saving performance and comfort. Accordingly, cross flow fans of high air volume, low energy consumption by a drive motor, and low noise level are in demand.
In order to reduce the level of noise, a conventional cross flow fan has a plurality of V-shaped notches that are open at the blade inner-circumferential edge along the longitudinal direction of the blade, and prevents occurrence of separation on the blade pressure suction surface in an outlet region using a vertical vortex generated at the notches, and thereby reduces the noise level (for example, see Patent Literature 1).